Saturday, November 30, 2013

Wintering Robins

Once robins have completed their breeding season - which may involve raising three broods - they begin to collect in flocks, often of hundreds, or even thousands of birds. As the season progresses, their diet shifts from animal protein during spring and summer (earthworms, grubs, insects and the like) to vegetable matter, principally fruit in the fall and winter.

These large flocks wander, roam, and migrate. My late October trip to Cape May coincided with the passage of robins through southern New Jersey. Huge numbers of robins fell out of the morning sky after their night flight, feeding on the junipers, winterberry, bittersweet, sumac, and other berries. (Not coincidentally, the robins’ descent into the trees and shrubs was followed by Sharp-shinned and Cooper’s Hawks.)

The American Robin is one of the most widespread, familiar, adaptable, and successful species in North America. Except for southern Florida, extreme southern Texas, and the southern  Arizona and California deserts, it breeds throughout the continent, north to the Arctic tree line. As winter approaches, it abandons its northern range and heads south.  Most range maps show it absent from the northern Rockies, northern Great Plains and most of New England in the winter. But not necessarily ... when I went to Montreal a few winters ago in pursuit of the Great Gray Owl, I also saw many wintering robins.

Unfortunately, that wonderful old piece of folklore about “Spring is on its way, I just saw the first robin” is not true. Robins can be found just about anywhere in the lower forty-eight during the winter. While typically wintering in large flocks, those flocks can be very nomadic; if their nomadic ways don’t intersect with our ways, then we conclude that they are not present - gone south.

The robins that nest in our neighborhood have probably gone south, while the hardier birds which breed far to the north, have moved down to replace them. But, through the whole continent, there is little variation in the American Robin (Turdus migratorius), an indication that breeding populations are constantly being mixed. Only in Sibley’s Guide are regional variations noted, and those variations are very minor - western robins have limited white tail corners - Atlantic Canada robins have a blacker nape and upper back.

Protein is essential to raising young, so "robins eat worms ..."

The species name, “migratorius,” does suggest that a characteristic of the robin is its migration. It wanders (migrates) all over the place.

The American Robin belongs to the thrush family, subfamily Turdinae, and the Genus Turdus. It is the only member of its Genus that any of us are likely to see. Rufous-backed Robin and Clay-colored Robin are accidental at a few places near the southern border, and the Fieldfare from Europe turns up in the East only on very rare occasions. The full and official common name is “American Robin,” but Turdus migratorius is so common that almost everyone knows what you are talking about when you talk about “robins.”

... but when protein is scarce, they turn to fruit and berries.

Nevertheless, we should never underestimate the ability of grammar to create confusion. When looking for information, I googled “winter  robin” and found many articles referring to, or even titled, “Winter Robin.”  “Winter Robin” sounds like the common name of a bird species, and I have had a couple of occasions when I have had to explain otherwise. “Winter robin” refers to an American Robin that is wintering in a wintery area - staying the winter, or being seen during the winter. It might better be referred to as a “wintering” robin. Not all robins abandon our north country and head south. Not all robins pass through our north country for more temperate winter climes. Some robins, probably from father north, stop here, and may even stay here for the winter. They are wintering.

You should not be surprised to see robins throughout the winter. They are warm-blooded. They have remarkable insulation from their down feathers. They can maintain body heat through a cold night by shivering. They can survive as long as they can get enough food during the day to replenish their stored fat reserves.

There are factors which will affect whether you see robins during the winter or not. The biggest correlation is snow cover. Data from the Great Backyard Bird Count done annually in mid-February indicates that the probability of seeing robins  drops “dramatically in areas with even just a few centimeters of snow cover.” Unusually low snow cover often results in unusually high numbers of robins, a pattern which has been seen over several years of accumulated data. It seems that robins, which are primarily ground feeders, avoid snow-covered areas.

Robins are self-sufficient and quite capable of finding their own food sources. If they appear around backyard feeders, it is because there is some other food source. They do not eat bird seed; their stomach and intestines are not designed to digest such food. Some people have enticed robins to bird feeders by putting out cut up fruits (apples, pears, cranberries, blueberries), softened dog food, or a variety of worms. The problem is that most robins have never heard of such a thing as a bird feeder. It just doesn’t occur to them to seek human handouts. It has been suggested that putting out “robin food” during severe weather might be helpful, but it is more likely that the squirrels will find the food before the robins do.

Do not be surprised if you see robins this winter. They are American Robins which are wintering - hence “wintering” robins. Their rattling call can brighten the dreariest of winter days, and should any of those winter days turn pleasant and mild, they are likely to burst into cheerful caroling.

Good birding!

Saturday, November 23, 2013

Diving Dabbler

Some years ago, I watched a Mallard diving in the Connecticut River, a observation which sent me to my library to research dabblers that dive. While not common, it does occur.

This past weekend, I saw dabblers diving again, this time repeatedly. I was along the Wissahickon Creek in Philadelphia. Several hen Mallards repeatedly dove. My vantage point was such that I could also see them swimming beneath the surface. Their surface activity was such, that this may have been part of their "bathing" and "preening" behavior, but the time they spent under water does not rule out the possibility that they were also feeding.

Drake Mallard watches as a hen dives beneath the surface.
Hen Mallard as she begins her dive.
Resurfacing, she shakes the water off her duck's back.
 Wood Ducks along the Wissahickon seem to have moved on, except for the lone male who has not completed his molt. When he stretched his wings, flight feathers on one wing appear to be missing, probably explaining his bachelorhood.

Good birding!!

Wednesday, November 20, 2013

Waterfowl Aggression

Songbirds finish their breeding season and head south. The boys hang with the boys, and the girls with the girls, and life is peaceful until Spring returns and hormones flow again.

Not so with the waterfowl. They head south, mix among their species, and seem to get right at the battle for the sexes. Yesterday in Cape May, I watched wild aggression among several American Wigeons. When my companion asked me what was going on, I replied, "A couple of men are fighting over a woman."

I'm not being sexist, nor stereotyping. It is what happens among wintering waterfowl.

This drake American Wigeon is not stretching his wings; he is posturing toward a rival male ...

Birds of North America describes it this way: "Intraspecific aggression (threatening posture, rushing, chasing, biting, bill grabbing, pushing, and pursuit flights) is a common component of courtship, pair formation, and territorial defense. Most aggressive encounters on the wintering grounds, during migration, and early in breeding season occur during courtship and pair formation between conspecific."

Here are three more photos of the aggressive behavior ...

On a trip to Cape May in late October, I watched Mute Swans engaged in the same aggression - a male trying to drive off a potential rival. Nearby, a female just watched.

Although a bit more subdued, this shows courtship/pair bonding between a drake and hen Gadwahl. No aggression here, but the drake lurking in the background may soon provoke other reactions ...

Open, raised bills are often part of waterfowl pair bonding - foreground, Gadwahl pair - a 2nd drake looks on
We do not need to wait until the Spring to watch avian antics motivated by sex. Just look for wintering waterfowl.

Good Birding!

Wednesday, November 13, 2013

Sanderling - a "True" Sandpiper

I love the seashore and beach most of the year. I am not too keen about the seashore during the summer when the sun is melanoma producing, and the sand is littered with debris that has drifted from inland and is scattered in nearly naked lumps all over the place. But in the fall, winter, and spring that debris has been gathered up and returned to its city scape. Then the seashore beach  is in its elemental form. The rising and falling tides stir the sands, smoothing them at the water’s edge, constantly reshaping the sandbars and dunes, and often casting up the ocean’s debris.

Sanderlings (and a few Dunlin)

In late October, I walked some beaches in Cape May, New Jersey. The low sun of the waning day glared off the placid waves. My long shadow preceded me as I walked slowly along the wet sand, just out of the water’s reach. Another lone walker was far ahead, apparently more intent on exercise than I was; her pace widened the distance between us. I allowed the distance to grow greater as I stopped and watched tiny white shorebirds chasing the waves.

Sanderlings run from the waves

Their legs were a blur as they ran up the sand ahead of the waves. Then they reversed direction to chase the water as it receded - back and forth, like school yard children playing tag - or teasing a playful dog on a leash. The birds I watched were Sanderlings,  and they are one of the reasons I love the beach along the seashore.

Sanderlings are common along our seacoasts except from mid-June to mid-July. During that period they are north of the Arctic circle, breeding. They waste little time in that task and are soon back along our coasts, chasing the waves. If you see a sandpiper on a sandy beach going back and forth with the water, barely getting its feet wet, you are seeing a Sanderling.

Audubon knew this bird as the Sanderling Sandpiper. Somewhere along the line, the mavens of nomenclature decided this was redundant, and dropped “sandpiper” from its name. But the Sanderling is arguably the only “true” sandpiper.

Sanderling - "birds that peep on the sand"
The “piper” part of “sandpiper” seems to come from a word meaning “chirp,” or “peep,” hence sandpipers are “birds that chirp on the sand,” or “peep on the sand.” The Sanderling and its closest relatives (in the genus Calidris) are known among bird watchers as “peeps.”

The Sanderling (meaning “little bird of the sand”) is the only sandpiper which you will regularly find on sand - or sandy beaches. I went through the Kaufman guide for the habitats where we are most likely to see other Calidris sandpipers. Here’s what I found:

Least Sandpiper - edges of rivers, ponds, marshes
Semipalmated Sandpiper - mudflats
Western Sandpiper - open flats
Pectoral Sandpiper - grassy mudflats, flooded fields (the “grasspiper”)
White-rumped Sandpiper - flooded fields, marshy edges of mudflats
Baird’s Sandpiper - grassy mudflats, flooded fields
Buff-breasted Sandpiper - short-grass plains, plowed fields
Dunlin - mudflats
Red Knot - tidal flats, sandy beaches
Purple Sandpiper - rocky coastlines, jetties
Spotted and Solitary Sandpiper (not genus Calidris) - along creeks and ponds

Most of these sandpipers will rest and sleep on sandy flats. On northbound migration, they feed on horseshoe crab eggs buried in the sandy beaches of the Delaware Bay. But their usual, preferred place for foraging, and where they are most often seen by the watchers of shorebirds, is not the sandy beach. Most would be more accurately termed “mudpipers.” But don’t expect any name changes in the near, or even distant, future. There is no requirement for accuracy in a common bird name.

The Sanderling is the exception. The Sanderling is a bird of the sand. It sleeps on sandy flats and forages at water’s edge on sandy beaches. It is a true “bird on the sand that peeps.”

The Sanderling is common, and it is very tempting to see it along a sandy beach - say to oneself, “Sanderling,” and go on to look for something else. But they merit leisurely watching. I stood watching them as the waves broke, spray flying. They were masters of timing - probing the sand, then nimbly running up the slope ahead of the water - then racing the water back down to grab new morsels stirred by the water’s action.

I watched a dozen Sanderlings probing wet sand where the tide had ebbed. Something sent them flying further down the beach. I walked closer to where they had been probing. Tiny little holes dotted the wet sand, an inch apart in random lines. My feet barely left a mark on the hard, wet surface. The tiny feet of the Sanderlings left no mark at all. Had I not been watching, this series of holes in the sand would have posed a mystery, causing me to wonder what could have caused these neat, uniform holes in the sand. But I had seen the Sanderlings.

Foreground: Sanderling in breeding plumage in May
Background: Ruddy Turnstone

Most of the year when we encounter Sanderlings, we see them in winter plumage. Then they are white, or gray-white, pale and chunky little birds. In Spring they molt into breeding plumage, briefly sporting a rich, reddish brown on head and foreparts. The times of transition from one plumage to the next present an array of in-between appearances. But whatever the plumage, Sanderlings are most likely to be on the sandy beach chasing the receding waters and speeding from the incoming waves.

On that Cape May beach, the Sanderlings were frenetic in their feeding, but fairly calm with my presence. By slow degrees, I inched closer. I could see them probe with open beak, gulp some tiny delicacy, always mindful of where the water’s edge was, whether to hurry toward the ocean or away from it.


And then suddenly, the flock took flight. In an instant, sixty birds disappeared over the dunes. In the corner of my eye, I saw a dark form. Almost as quickly as I could lift my binoculars, the dark form had also disappeared beyond the dunes. I could only get a feel of pointed wings, but it was enough. Sanderlings were foraging along the shoreline in the late afternoon. So was the Merlin. I had watched Sanderlings ingesting energy against the chilly autumn night. And now I wondered if the Merlin, a falcon of the north, would also be feeding.

I can’t choose between the two, and have no right to do so anyway. So I wished the Sanderlings - and the Merlin - good luck and good feeding.

The seashore birding that late October afternoon was very good.

Sanderlings take flight

Saturday, November 09, 2013

Heinz National Wildlife Refuge

This week I made my first Fall visit to John Heinz National Wildlife Refuge at Tinicum. Nearly every visit to this small refuge evokes in me a mental disconnect. It is in the City of Philadelphia. I have been in Center City on occasions when the only bird life to be seen was the House Sparrow. Even pigeons were absent.

By contrast, Heinz refuge is a haven for scores of species - living, breeding, migrating. This is waterfowl season, and there were large flocks of dabblers and divers feeding on the impoundment ... until something puts them into the air, like the resident eagle passing overhead ...

Northern Shovelers and Green-winged Teal at Heinz Refuge
When we "zoom out" on the flocks in the above photo, we get a feel for the number of waterfowl present, and the "disconnected context" of the refuge. In the not too distant background are the garages, terminals, control tower, and hotel of the Philadelphia International Airport ...

The trail around the impoundment borders the far end of the water visible in the above photo and within a few yards of freight rail lines and commuter lines ...

Turning around from the above sights, I have had my best sightings anywhere of Rusty Blackbirds, and along the same trail have had great photo ops for Golden-crowned and Ruby-crowned Kinglet, Brown Creeper, Northern Saw-whet Owl, and others.

This week it was Greater Yellowlegs that was close at hand. I have had numerous good photos op for this shorebird, but not recently. Seize the opportunity ...

Greater Yellowlegs
Greater Yellowlegs
Center City Philadelphia from the refuge
Eventually there was sun, and wonderful Fall colors, and all only minutes from the financial heart of a major city.

Good Birding!


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